Magnetic bead based immunoassay for enumeration of CD4+ T lymphocytes on a microfluidic device.

Human immunodeficiency virus (HIV) diagnostics are urgently needed in resource-scarce settings. Monitoring of HIV-infected patients requires accurate counting of CD4(+) T lymphocytes. However, the current methods for enumeration of CD4(+) T lymphocytes are of high cost, technically complex and time-consuming. In this paper, we developed a simple, rapid and inexpensive one-step immunomagnetic method for separating and counting CD4(+) T lymphocytes on microfluidic devices with enlarged reaction chambers. CD4(+) T lymphocytes were successfully separated and captured from the cell suspension obtained from mouse thymus. CD4 counts were determined under an optical microscope in a rapid and simple format. In order to acquire the maximum efficiency of cell capture, relative parameters were investigated, including section area of the reaction chamber and injection flow rate of the cell suspension. The enlarged reaction chamber with two symmetrical cone-shaped ends was helpful for cell capture, and the maximum capability of captured CD4(+) T lymphocytes was about 700 cells microL(-1). Our investigations avoided the complex sample pre-treatment, and the entire analysis time was significantly reduced to 15 min. This CD4 counting microdevice had the potential to reduce the cost for HIV diagnosis in resource-limited settings.